We have altered the formation and function of photoreceptor discs of the retina of rats raised on essential fatty acid (EFA) deficient diets. In addition, rats raised for several generations on EFA deficient diets have an altered fatty acid composition. The following research program relating structure, function and chemistry of photoreceptor cells is proposed: 1. To study the metabolism of lipids in rod photoreceptor membranes and rod visual cells. 2. To study the specific effects of polyunsaturated fatty acids and other components on the structure and function of photoreceptor membranes. 3. To study the mechanisms that control the biosynthesis of rod photoreceptor membranes. 4. To study the effects of EFA deficiency or antimetabolite therapy on the vision of humans. 5. To apply the information obtained from normal animals to the management of retinal degeneration in the RCS rat. The above studies will be done by autoradiographic, biochemical and electrophysiological techniques.